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Identification of a novel trigger complex that facilitates ribosome-associated quality control in mammalian cells.

ABSTRACT: Ribosome stalling triggers the ribosome-associated quality control (RQC) pathway, which targets collided ribosomes and leads to subunit dissociation, followed by proteasomal degradation of the nascent peptide. In yeast, RQC is triggered by Hel2-dependent ubiquitination of uS10, followed by subunit dissociation mediated by the RQC-trigger (RQT) complex. In mammals, ZNF598-dependent ubiquitination of collided ribosomes is required for RQC, and activating signal cointegrator 3 (ASCC3), a component of the ASCC complex, facilitates RQC. However, the roles of other components and associated factors of the ASCC complex remain unknown. Here, we demonstrate that the human RQC-trigger (hRQT) complex, an ortholog of the yeast RQT complex, plays crucial roles in RQC. The hRQT complex is composed of ASCC3, ASCC2, and TRIP4, which are orthologs of the RNA helicase Slh1(Rqt2), ubiquitin-binding protein Cue3(Rqt3), and zinc-finger type protein yKR023W(Rqt4), respectively. The ATPase activity of ASCC3 and the ubiquitin-binding activity of ASCC2 are crucial for triggering RQC. Given the proposed function of the RQT complex in yeast, we propose that the hRQT complex recognizes the ubiquitinated stalled ribosome and induces subunit dissociation to facilitate RQC.

SUBMITTER: Hashimoto S

PROVIDER: S-EPMC7042231 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature

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Identification of a novel trigger complex that facilitates ribosome-associated quality control in mammalian cells.

Hashimoto Satoshi S Sugiyama Takato T Yamazaki Reina R Nobuta Risa R Inada Toshifumi T

Scientific reports 20200225 1

Ribosome stalling triggers the ribosome-associated quality control (RQC) pathway, which targets collided ribosomes and leads to subunit dissociation, followed by proteasomal degradation of the nascent peptide. In yeast, RQC is triggered by Hel2-dependent ubiquitination of uS10, followed by subunit dissociation mediated by the RQC-trigger (RQT) complex. In mammals, ZNF598-dependent ubiquitination of collided ribosomes is required for RQC, and activating signal cointegrator 3 (ASCC3), a component ...[more]

PMID: 32099016

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Project description:Translation elongation rates are regulated to ensure proper conformation and biological function of proteins. Translation of either non-stop mRNA or transcripts coding for poly-basic sequences induces ribosome stalling, and the arrest product is degraded by the ribosome-mediated quality control system (RQC). During this process, the stalled ribosome is dissociated into subunits, and the polypeptide is ubiquitinated by the E3 ubiquitin ligase Listerin on the 60S large ribosomal subunit (LSU) leading to subsequent proteasomal degradation. However, it is largely unknown how stalled ribosomes are recognized and dissociated into subunits. Here we report that ubiquitination of the ribosomal protein uS10 by the E3 ubiquitin ligase Hel2 is required for the production of the RQC substrate. RQC-trigger (RQT) factors, a RNA helicase-family protein Slh1/Rqt2, ubiquitin binding protein Cue3/Rqt3 and yKR023W/Rqt4, were also required for the primary steps of RQC, and associated with Hel2-ribosome complexes. Rqt2-4 factors were dispensable for the ubiquitination of uS10 by Hel2/Rqt1 and associated with ribosomes independent of the ubiquitination of uS10. However, the ubiquitin-binding activity of Rqt3 were crucial to trigger RQC. Cryo-electron microscopy (cryo-EM) analysis revealed that Hel2 bound ribosomes are in an rotated state containing hybrid state AP- and PE-tRNAs. Furthermore, ribosome profiling revealed that short footprints, hallmarks of hybrid state ribosomes18, were accumulated at tandem CGA rare codons at the beginning of the poly arginine stalling sequence and long footprints at subsequent codons, respectively. Short footprints at CGA codons were decreased in rqt1 mutant but drastically increased in uS10 mutants defective in the ubiquitination or rqt2 mutant. Collectively, our results demonstrate that Hel2 stabilizes ratcheted ribosomes leading to ubiquitination of uS10. Subsequently, Rqt2-4 factors target these hybrid state ribosomes specifically, allowing subsequent RQC reactions.

Dataset Information

Identification of a novel trigger complex that facilitates ribosome-associated quality control in mammalian cells.

Publications

Identification of a novel trigger complex that facilitates ribosome-associated quality control in mammalian cells.

Similar Datasets

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